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I need help with emission test


allan911

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:help: :help: I have failed TWo emissions tests (in Denver) for CO for my 1990 C4. This car passed with a zero CO in Nevada two months ago. My first test (at 2500 rpm) was 1.70 PPM CO (1.2 is maximum allowable), then I changed oil, changed the O2 sensor (Bosch Porsche replacement) and changed the air filter which was dirty (replaced stock with a K&N) and the second emissions test came back at 2.7 PPM CO!!!. What happened? Car was at operating temperature for second test (hot) and a little cooler for first test.

I have also run injector cleaner and Bluesky additive through the car as well. Is there something I need to do to pass CO test at 5600 feet elevation? does the car need to go to a Porsche dealer.

I'd appreciate any help, thanks

Edited by allan911
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One more question regarding the O2 sensor. If the O2 sensor is not completely plugged in will a warning light come on? It was pretty difficult plugging the new sensor back into the plug and I am not 100% positive I got all three contacts plugged in.

I forgot to take a picture of the plugg assembly before I unplugged it to remove the old O# sensor. The car has only 58k miles.

thanks for your help :help:

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It looks like the O2 sensor was NOT plugged in correctly, but no CEL came on. Should the CEL come on if the O2 sensor is not plugged in?

One more question regarding the O2 sensor. If the O2 sensor is not completely plugged in will a warning light come on? It was pretty difficult plugging the new sensor back into the plug and I am not 100% positive I got all three contacts plugged in.

I forgot to take a picture of the plugg assembly before I unplugged it to remove the old O2 sensor. The car has only 58k miles.

thanks for your help :help:

Edited by allan911
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So, if I understand you correctly, even though I may not have had the O2 sensor plugged in, the CEL might not have come on. Being that my O2 reading went from 1.7 PPm to 2.7 PPM, I am thinking that the O2 sensor was not working.

Do you have any other suggestions to get my emissions test in compliance?

BTW, I have since plugged the O2 sensor in and the car is running MUCH better.

thanks,

Mark

Not if the problem(s) corrects itself within the DME program/emmisions specified time period.
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Where are you located?

After replacing an O2 sensor you need a certain number of drive cycles for all of the "pending" codes to be cleared. In most states (like California) the smog/emissions tests require no pending codes (That's how they know that you didn't just clear the code for the test - and it will come back later).

Most daily driven cars should clear any pending codes in 3 to 5 days of normal driving.

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I am located in Denver, Colorado.

I have driven the car twice since installing the new O2 sensor (and plugging it in correctly).

I just failed the third emissions test registering 1.8 PPM CO. Plugging in the O2 sensor definitely helped, but I am still not making the maximum 1.2 PPM CO allowable.

The car passed Nevada emissions with flying colors, but can't seem to make the CO test here at 5700' elevation.

If anyone out there knows a trick to pass CO emissions in Denver, please let me know. The HC levels were low at both idle and 2500 RPM, NOX was fine as well.

thanks

Where are you located?

After replacing an O2 sensor you need a certain number of drive cycles for all of the "pending" codes to be cleared. In most states (like California) the smog/emissions tests require no pending codes (That's how they know that you didn't just clear the code for the test - and it will come back later).

Most daily driven cars should clear any pending codes in 3 to 5 days of normal driving.

Edited by allan911
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:clapping: For everyone's information who might need help passing an emissions test on a Porsche 911. :clapping:

I FINALLY PASSED! (after failing 3 times). I changed the O2 sensor, changed the oil, changed the air filter and re-set the fuel selector switch in the DME (accessible from the outside) to position #3 (lean).

The previous test was 1.85 PPM CO (1.2 PPM allowable), after the modifications, the last test came back at 0.7 PPM. I also tested in the cool morning (60F) versus 85F - 90F to help increas air density (and improve air/fuel ratio at 5700' elevation).

thanks for the help :clapping:

I am located in Denver, Colorado.

I have driven the car twice since installing the new O2 sensor (and plugging it in correctly).

I just failed the third emissions test registering 1.8 PPM CO. Plugging in the O2 sensor definitely helped, but I am still not making the maximum 1.2 PPM CO allowable.

The car passed Nevada emissions with flying colors, but can't seem to make the CO test here at 5700' elevation.

If anyone out there knows a trick to pass CO emissions in Denver, please let me know. The HC levels were low at both idle and 2500 RPM, NOX was fine as well.

thanks :clapping:

Where are you located?

After replacing an O2 sensor you need a certain number of drive cycles for all of the "pending" codes to be cleared. In most states (like California) the smog/emissions tests require no pending codes (That's how they know that you didn't just clear the code for the test - and it will come back later).

Most daily driven cars should clear any pending codes in 3 to 5 days of normal driving.

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